Translation

Then that supreme authority, personified by sound and unseen by eyes, but most wonderful, stopped speaking. Feeling a sense of gratitude, I offered my obeisances unto Him, bowing my head.

Purport

That the Personality of Godhead was not seen but only heard does not make any difference. The Personality of Godhead produced the four Vedas by His breathing, and He is seen and realized through the transcendental sound of the Vedas. Similarly, the Bhagavad-gītā is the sound representation of the Lord, and there is no difference in identity. The conclusion is that the Lord can be seen and heard by persistent chanting of the transcendental sound.